During manufacture of items that include an assembly of components or workpieces, often a three-dimensional (3D) model of each component is generated, and then the components are virtually assembled using the 3D models to assess the manufactured item prior to actually building the item.
A 3D model of a component may be generated using a structured light scanner to scan the component. When the component includes a hole, such as a drilled hole for attaching a fitting for example, a target is generally attached or coupled to the hole during the scanning process to enable identification of a location or position of the hole within the scanned data as well as determination of a hole vector. The position of the hole may be necessary to enable virtual assembly of the components that are scanned separately so that the components are lined up by the holes for coupling.
Existing photogrammetry targets for use in determining hole position and hole vectors can create some uncertainty in hole position due to the fact that the targets generally use only one to two scanned points to generate a vector. For instance, with a single-point target, projection of a location of the scanned single point target can offer error if the hole is not normal to the local surface due to only one scanned data point. With two-point targets, the use of two scanned points to generate a line to define a centerline of the target for the vector hole position is possible, but this can lead to error in a predicted surface position and direction of the hole to the extent that one of the points becomes blocked or shadowed. In addition, with either the single or two point target, the target should be properly oriented relative to the scanner, otherwise, the scanner may introduce some inaccuracies in the vector calculation.
Using a structured light scanner to scan a component without use of a target can be performed to try to find a position of a hole, but determination of the hole position and hole vector would be difficult and lack high accuracy due to unknown direction and/or orientation of the hole. Other factors that may affect the difficulty include that the structured light scanner may not detect reflective surfaces that typically remain after machining holes when the components are metal, and for holes of a smaller size it can be difficult to capture enough interior surface data to compute an accurate hole position and hole vector.
What is needed is a scanning target for use with surface scanners, such as structured light scanners, that enables determination of the position and vector of holes within components to a high degree of accuracy.